The claimed systems and methods relate generally to loudspeaker teleconferencing systems that utilize full duplex operation with distant participants, and more particularly to teleconferencing pods that can connect to a telephone device generating an intermittent sidetone that is active at certain times not in the control or monitoring of the pod, wherein the pod includes a sidetone suppressor and compensation function to avoid applying suppression in the absence of an externally-generated sidetone.
The inventions described herein relate to conferencing systems that can connect to a telephonic device in systems such as that depicted in FIG. 1. In that system 100, a telephonic connection is made between a local participant in proximity to a conferencing pod 102 and a distant party 108 using distant party equipment and/or devices, not shown. In system 100, a telephonic device 104 is used to make a connection 107 with distant party 108. Herein the term telephonic and telephone refer not only to devices and systems that utilize a public switched telephone network (PSTN), but also other devices that can make an audio connection between a local participant and a distant participant through any kind of network or connection including point-to-point, wired, wireless, switched packet and any other. The telephonic device 104 includes a keypad and/or controls 106 for controlling the connection 107 to distant party 108 and optionally other controls such as volume, mute and others. Conferencing pod 102 may connect to device 104 by simulating another device type such as a headset. Hereinafter the term “connector” includes not only physical connections, but also terminals and contacts of any type, and also digital, network, wireless or virtual connections.
Telephonic device 104 may produce a sidetone. The term sidetone has several historical meanings, and originates from the early days of radio when Morse code was used. To provide feedback to the radio equipment operator and audible tone was produced in a headset worn by the operator at times when the transmit key was depressed. In devices using an audio signal the term sidetone has come to mean a retransmission of an audio signal received at a local microphone to a local participant, for example through a headset. This is done as feedback to the local participant that his words are being transmitted. Sidetone generation and use can be understood in reference to FIG. 2A, wherein a simple telephonic device is illustrated. The device of FIG. 2A is a stand-alone telephonic device, with an incoming port 208 and an outgoing port 206 for carrying audio to and from a distant participant. This device also includes a speaker 202 and a microphone 200. Speaker 202 and microphone 200 would ordinarily be made part of a headset or other equipment whereby speaker 202 is positioned near the ear of local participant 204, and the sound of 213 produced by speaker 202 is not substantially carried to microphone 200.
Where sound produced by the Speaker 202 is not being carried to microphone 200 it may be desirable to include a sidetone generator 210. The sidetone generator produces an audio signal received at the microphone 200 at a low level, typically less than what listener 204 hears a distant participant, providing feedback to the listener 204 that his speech is being transmitted to the distant parties. That audio signal is fed to a mixer 212 along with the distant audio received at port 208 producing a signal at speaker 202 that includes both the distant audio and a sidetone.
Now referring to FIG. 2B, the functional aspects of a system as shown in FIG. 1 are illustrated. The system of FIG. 2B includes a telephone device having many of the same components as that of the stand-alone device, including an incoming port 208, an outgoing port 206, a sidetone generator 210 and the mixer 212. Although this telephone device might include a speaker and microphone, here a connection is made to a separate device through an incoming connector 216 and an outgoing connector 214 which supplies an incoming and outgoing audio signal to an external device, for example a headset. The external device connects to connectors 214 and 216, and includes its own speaker 203 and microphone 201. If the external device is a conferencing pod, speaker 203 will be configured to produce sound in the local vicinity so that the local participants 204 can hear the distant audio received at port 208. Microphone 201 is likewise configured to pick up sound in the local vicinity of the pond such that the local participants can be heard by the distant parties.
The presence of sidetone generator 210 introduces a problem. The inclusion of sidetone generator 210 in the telephonic equipment may be on an assumption that external equipment connected to ports 214 and 216 is a headset, or rather that a substantial transmission path does not exist between the speaker and microphone at the external device. However, the presence of a conferencing pod does indeed introduce such a path 222. Thus, distant audio produced at Speaker 203 is carried to microphone 201 and transmitted over path 222 through the outgoing connector 260 distant participants. This is perceived by the distant participants as an echo with the delay approximately two times the propagation delay between the local and the distant participants. Additionally, because of the presence of a sidetone generator 210 a feedback loop is introduced in the local equipment. This is experienced by the local participants and the distant participants as ringing and, if the coupling between speaker 203 and microphone 201 is sufficient, howling.
Therefore, the situation presented in FIG. 2B illustrates a particular problem where a conferencing pod is to be connected to a telephone in substitution of a headset, although that is not the only situation that the inventions which are described herein may be applied to. However, the situation provides a convenient illustration to describe the configuration and operations described in the discussion below.